Hydrogeochemical characteristics of karst groundwater in Jinci spring area, north China

Integration of the information from hydrochemical data, statistical analysis and modeling technique is crucial for extending our knowledge of hydrochemistry of karst aquifers. In this paper, conventional graphical methods, statistical analysis and PHREEQC inverse modeling were used to investigate the hydrogeochemical characteristics and evolution processes of karst groundwater in Jinci spring area. The results showed that the dominant hydrochemical types of karst groundwater determined by Piper diagram were Ca·Mg–SO4·HCO3, Ca·Mg–SO4, Ca–SO4, Ca–SO4·HCO3 and Ca–HCO3, and the main components of karst groundwater were dominated by rock–water interactions based on statistical analysis. Ca2+, Mg2+ and HCO3− originated mainly from the dissolution of calcite and dolomite; SO42− came mostly from gypsum dissolution and pyrite oxidation; and the source of Na+ and Cl− could either be major from halite dissolution or cation exchange. Moreover, PHREEQC inverse modeling indicated that calcite, gypsum and CO2 (g) were dissolved, and Ca–Mg exchange prevailed along the flow path (from recharge area to runoff area); the dissolution of gypsum, dolomite and CO2 (g), and halite precipitation, and Na–Mg and Ca–Mg exchange occurred along runoff area to discharge area; and there were the dissolution of carbonate, gypsum, halite and CO2 (g), Na–Mg and Ca–Mg exchange from deep buried area to discharge area.